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%0 Thesis %A Chatziliadou, Maria %T Rb-Sr Alter und Sr-Pb Isotopencharakteristik von Gangmineralisationen in paläozoischen Gesteinen am Nordrand des linksrheinischen Schiefergebirges (Raum Stolberg-Aachen-Kelmis) und Vergleich mit den rezenten Thermalwässern von Aachen-Burtscheid %C Aachen %I Publikationsserver der RWTH Aachen University %M RWTH-CONV-113503 %P VIII, 144, [ca. 150] Bl. : Ill., graph. Darst. %D 2009 %Z Zusammenfassung in dt. und engl. Sprache %Z Aachen, Techn. Hochsch., Diss., 2009 %X Vein mineralizations of different age and formation were studied in the northern Eifel area and its foreland. The focus was put on microstructure, geochemistry and isotopic composition to characterize discrete fluid flow events and to date their generations. Samples from the geothermal well RWTH – 1 representing Variscan vein mineralizations, from the Pb – Zn vein mineralizations of the mining district Stolberg – Aachen – Kelmis with special emphasis on veins from the limestone quarry Hastenrath of Postvariscan age and from the recent thermal springs of Aachen and Burtscheid were investigated. RWTH – 1 sank down in the town of Aachen in 2004 is situated within the Aachen fold and thrust belt and reached a final depth of 2544 m. From top to the base the bore hole exposed Upper Carboniferous, Upper Devonian and Lower Devonian carbonate and siliciclastic sediments. Three core cuts display intensive hydrothermal veining with variable orientations. These veins are mm to cm wide and represent extension structures with characteristics of deformation and recrystallization in minerals of the rim parts. Calcite, ankerite, dolomite, chlorite, quartz and occasionally pyrite are the typical vein minerals with chlorite found along the vein margins and the carbonates generally in the centre. Crack-seal processes indicate brittle deformation and multiple reactivations of the opening. The chemical compositions of the chlorite from veins of the first and second cored section of the well indicate formation temperatures of 290°C to 370°C. Homogenization temperatures of fluid inclusions found in the vein minerals are < 390°C (Lögering, 2008). These temperatures reflect typical Variscan metamorphic temperatures along the northern part of the Rhenohercynian fold belt (Behr et al., 1993, Muchez et al., 2000). The precipitation of the carbonate minerals within the veins is attributed to cooling of a fluid phase and its change in pH by reaction with the carbonate-bearing wall rocks during uprise in the fault systems of the rocks (compare also Lögering, 2008). The pronounced factionation of rare earth elements suggests that the components of the precipitated carbonate minerals in the veins cannot be derived from the immediate wall rocks aside the veins but must have come from more distant rock volumes. Independant from the stratigraphic level these carbonates are characterized by a significant Eu anomaly which is interpreted to show a carbonate formation at increased temperatures. Initial 87Sr/86Sr ratios of calcite and chlorite of the veins cannot become identical at any times. Thus a Rb-Sr isochrone age of the mineral assemblage of the veins cannot be obtained. Model calculations for the chlorite – carbonate mineral pairs using a paleo-mixing of different Sr isotope compositions suggest a model age of 218±15 Ma (Beiss, 2008) which is similar to 40Ar/39Ar ages of the vein chlorites of 182±18 Ma (Sindern et al., 2008). Of course these äges" do not correspond to the Variscan formation of the veins. The initial 87Sr/86Sr ratios of carbonate minerals and chlorite, both from the veins, and the fractions of the corresponding host rocks soluble in HCl show a considerable variation for Carboniferous times. Calcite varies from 0,71107±1 to 0,72119±1, Chlorite from 0,71513±4 to 0,72628±3 and the soluble part of the host rocks from 0,71049±1 to 0,72138±1. This variation in Sr composition may be an effect of intensive interaction of the fluid phase with the corresponding wall rocks of the veins but can also be interpreted as distinct fluid pulses with individual Sr compositions. In any case, since chlorite is always higher in 87Sr/86Sr than the associated carbonates the two phases cannot be precipitated simultaneously. Chlorite may have formed by interaction of a fluid phase with the country rocks or, chlorite experienced a late alteration. Likewise, the carbonate components are not exclusively derived from the wall rocks. Pb isotope compositions of pyrite (206Pb/204Pb = 18,229 – 18,254; 207Pb/204Pb = 15,589 – 15,592) characterize the Variscan mineralizations. The Lower Carboniferous limestone of the Hastenrath quarry shows 87Sr/86Sr ratios of 0,70812±1 and 0,70817±1 which is typical for a marine formation. For the source of C delta13C of this rock suggests formation waters. Diagenetic processes within this limestone are documented by small-scale branching structures composed of dolomite. The structures are cross cut by non-oriented calcite veins with Sr isotope compositions distinctly higher radiogenic than the surrounding country rocks. Sr of these veins has an unknown source. The structures of the Paleozoic limestones are block faulted perpendicular to their strike by NW –SE trending faults which exhibit a Pb – Zn vein mineralization typical for the Stolberg – Aachen – Kelmis mining district. Three different mineralized zones can be distinguished within the veins (zones 1, 2, 3) which indicate at least three crack – seal processes and thus at least three periods of fluid flow. The brecciated zone 1 marks the first fracture sealing process. It contains fragments of galena crystals, chalcopyrite, bornite, quartz, dolomite, ankerite and blocks of the wall rocks fixed in a calcitic matrix. The second fracture sealing phase (zone 2) is composed exclusively of large crystals of calcite. Zone 3 is made of calcite which is overgrown by collomorphic sphalerite. Within this ZnS inclusions of galena, chalcopyrite and bornite are found. In parts of the sphalerite the Cd content is very high (up to 6,5 wt.- %K Mineralchemie (SWD) %K Geochemie (SWD) %K Datierung (SWD) %K Isotopendatierung (SWD) %K Vererzung (SWD) %K Zinkblende (SWD) %K Carbonate (SWD) %F PUB:(DE-HGF)11 %9 Dissertation / PhD Thesis %U https://publications.rwth-aachen.de/record/51191